The worst is when you win the first round of domination, and barely lose the second one. Why the hell is that a loss? Its a tie, you've both won a round.

But yeah, I've had my fair share of joining a team which has no hope of winning.

It's just a "half-time" swap over not a round based match if you know what I mean. The scores don't reset or anything, you just carry on score wise.

Regarding the OPs query, even if you back out if your then still possibly going to get thrown into yet another total loss of a game, hop out again and you'll get hit with probation. So your really better off just joining and doing your best. At least you'll have a fresh new series of games waitin for you when its over. The only thing that annoys me is when I hop into a losing game and then the lobby closes making me go through the whole charade again and again.